An interface circuit for an integrated injection logic circuit comprises a current mirror circuit having its input current value set by a first resistor and its input controlled by an output signal of the integrated injection logic circuit, a second resistor connected to a current path at the output side of the current mirror circuit, and output means connected to the current output terminal of the current mirror circuit.

Patent
   4485318
Priority
Mar 18 1981
Filed
Mar 10 1982
Issued
Nov 27 1984
Expiry
Mar 10 2002
Assg.orig
Entity
Large
2
7
all paid
1. An interface circuit for use with an integrated injection logic circuit, comprising:
first and second power source terminals;
first and second resistors each having a first end connected to said first power source terminal;
a current mirror circuit connected to said integrated injection logic circuit and having an input current path and an output current path, said input and output current mirror paths being respectively connected between said second power source terminal and the respective second ends of said first and second resistors, and whereby the input current value of said current mirror circuit is set by said first resistor and the input of said current mirror circuit is controlled by the output signal of said integrated injection logic circuit; and
output means connected to said second end of said second resistor.
5. An interface circuit for an integrated injection logic circuit, comprising:
first and second power source terminals;
first, second and third resistors each having a first end connected to said first power source terminal;
a first current mirror circuit connected to said integrated injection logic circuit and having an input current path and an output current path, said input and output current mirror paths being respectively connected between said second power source terminal and the respective second ends of said first and third resistors, whereby the input current value of said first current mirror circuit is set by said first resistor and the input of said first current mirror circuit is controlled by the output signal of said integrated injection logic circuit;
a second current mirror circuit having an input current path and an output current path, said input and output current mirror paths being respectively connected between said second power source terminal and the respective second ends of said second and third resistors, and whereby the input current value of said second current mirror circuit is set by said second resistor; and
output means connected to said second end of said third resistor.
2. The interface circuit for an integrated injection logic circuit according to claim 1, in which said output means includes an emitter follower circuit comprising a transistor having its base connected to the second terminal of said second resistor and a resistor connected between the emitter and the second power source terminal.
3. The interface circuit according to claim 1, wherein said current mirror circuit comprises a first transistor, which has a collector and a base both connected to said second end of said first resistor and an emitter connected to said second power source terminal, and a second transistor, which has a collector connected to said second end of said second resistor, a base connected to said base of said first transistor and an emitter connected to said second power source terminal.
4. The interface circuit according to claim 3, wherein an emitter circuit of at least one of said first and second transistors includes a third resistor.
6. The interface circuit for an integrated injection logic circuit according to claim 5, in which said output means includes an emitter follower circuit comprising a transistor having its base connected to the second terminal of said third resistor and an emitter resistor.
7. The interface circuit according to claim 5, wherein said first current mirror circuit comprises a first transistor, which has a collector and a base both connected to said second end of said first resistor and an emitter connected to said second power source terminal, and a second transistor, which has a collector connected to said second end of said third resistor, a base connected to said base of said first transistor and an emitter connected to said second power source terminal, and wherein said second current mirror circuit comprises a third transistor, which has a collector and a base both connected to said second end of said second resistor and an emitter connected to said second power source terminal, and a fourth transistor, which has a collector connected to said second end of said third resistor, a base connected to said base of said third transistor and an emitter connected to said second power source terminal.
8. The interface circuit according to claim 7, wherein an emitter circuit of at least one of said first to fourth transistors includes a fourth resistor.

This invention relates to an interface circuit for an integrated injection logic circuit as used in an interface between the integrated injection logic circuit and the other circuit.

A fundamental circuit of the integrated injection logic circuit (I2 L circuit) comprises, as shown in FIG. 1, a PNP transistor QI as an injector and an output NPN transistor Q0 having at least one open collector. Since a greater load cannot be driven with one transistor Q0, an interface circuit is required for the I2 L circuit to drive the other circuit, for example, a TTL circuit.

FIGS. 2 and 3 each show a conventional interface circuit as used in an interface circuit between an I2 L circuit and a TTL circuit. The interface circuit as shown in FIG. 2 comprises three NPN transistors Q1 to Q3, three resistors R1 to R3 and one diode D1. An output of an I2 L inverting gate G as configured in FIG. 1 is applied to the base of the NPN transistor Q1. The interface circuit as shown in FIG. 3 comprises two PNP transistors Q4, Q5, two NPN transistors Q6, Q7 and seven resistors R4 to R10. An output of an I2 L inverting gate G as configured in FIG. 1 is applied through the resistor R5 to the base of the PNP transistor Q4. In the conventional interface circuit it is not possible to obtain an arbitrary output voltage and there is a disadvantage that high and low level output voltages are fixed to certain levels. In the interface circuit of FIG. 2, for example, a high level output voltage is VCC -2VF and a low level output voltage is VCE (sat) (Q3). In the interface circuit as shown in FIG. 3 the high level output voltage is VCC -VCE (sat)(Q5)-VBE (Q7) and the low level output voltage is zero (ground potential).

It is accordingly an object of this invention to provide an interface circuit for an integrated injection logic circuit which can freely set the value of an output voltage.

According to this invention there is provided an interface circuit for an integrated injection logic circuit comprising a first resistor, a current mirror circuit having its input current value set by a first resistor and having its input controlled by an output signal of the integrated injection logic circuit, a second resistor inserted in an electric current path at the output side of the current mirror circuit, and an output means connected to the output terminal of the current mirror circuit.

According to another embodiment of this invention there is provided an interface circuit for an integrated injection logic circuit which comprises a first resistor, a first current mirror circuit having its input current value set by the first resistor and having its input controlled by an output signal of the integrated injection logic circuit, a second current mirror circuit connected to receive an input current set by a second resistor and having its current output terminal connected at a common junction to a current output terminal of said first current mirror circuit, a third resistor connected to a common current path at the output side of the first and second current mirror circuits, and input means connected to the common current path of the first and second current mirror circuits.

FIG. 1 is a circuit diagram showing a fundamental circuit of an I2 L circuit;

FIG. 2 is a conventional interface circuit as used in an interface between an I2 L circuit and a TTL circuit;

FIG. 3 is a conventional interface circuit as used in an interface between an I2 L circuit and a TTL circuit;

FIG. 4 is an interface circuit for an integrated injection logic circuit according to one embodiment of this invention; and

FIGS. 5 to 9 each show an interface circuit for an integrated injection logic circuit according to another embodiment of this invention.

FIG. 4 shows an interface circuit for an integrated injection logic circuit according to one embodiment of this invention. The FIG. 4 circuit comprises two current mirror circuits M1, M2, an NPN transistor Q15 and four resistors R11 to R14. The current mirror circuit M1 comprises two NPN transistors Q11, Q12 having their bases connected in common and their emitter areas equal to each other. The emitters of the NPN transistors Q11, Q12 are each connected to ground and the collector-to-base path of the NPN transistor Q11 is short-circuited. Likewise, the other current mirror circuit M2 comprises two NPN transistors Q13, Q14 having their bases connected in common and their emitter areas equal to each other. The emitters of the NPN transistors Q13, Q14 are grounded and a collector-to-base path of the NPN transistor Q14 is short-circuited. To a common junction of the bases of the NPN transistors Q11, Q12 in the current mirror circuit M1 is connected an output terminal of an I2 L inverting gate G at an output stage of the I2 L circuit. A resistor R11 is connected between the collector of the NPN transistor Q11 at the input side of the current mirror circuit M1 and the positive terminal of a power source VCC to set an input current value I1 of the current mirror circuit M1. Likewise, a resistor R12 is connected between the collector of the NPN transistor Q14 at the input side of the other current mirror circuit M2 and the positive terminal of the power source VCC to set an input current value I2 of the current mirror circuit M2. The collectors of the NPN transistors Q12, Q13 at the output side of both the current mirror circuits M1, M2 are connected to each other and a resistor R13 is connected between a junction P of the collectors of the transistors Q12, Q13 and the positive terminal of the power source VCC. The NPN transistor Q15 and emitter resistor R14 of the transistor Q15 constitutes an emitter follower output circuit and the base of the NPN transistor Q15 in the emitter follower output circuit is connected to the junction point P. An output terminal Out is connected to the emitter of the NPN transistor Q15 and also to the input terminal of the other circuit such as a TTL circuit.

The operation of the interface circuit will be explained below.

With the I2 L inverting gate G ON i.e. the NPN transistor Q0 of FIG. 1 ON, an electric current I1 through the resistor R11 flows into the I2 L inverting gate G, causing the NPN transistors Q11, Q12 to be cut off. As a result, the current mirror circuit M1 is not operated. Since an electric current I2 set by the resistor R12 flows into the input side of the current mirror circuit M2, an electric current I2 of the same value also flows at the output side of the current mirror M2. That is, the electric current I2 flows through the resistor R13. With the base-to-emitter voltage of the NPN transistor Q15 represented by VBE (Q15), an output voltage VO on the output terminal Out is given by the following equation:

VO =VCC -I2 ·R13 -VBE (Q15) (1)

That is, the output voltage VO is equal to value by subtracting a voltage drop I2 ·R13 through the resistor R13 and base-to-emitter voltage VBE (Q15) of the NPN transistor Q15 from the power source voltage VCC. At this time, the value of the output voltage VO corresponds to a value at the high level output time.

With the I2 L inverting gate G OFF, the electric current I1 through the resistor R11 flows through the current mirror circuit M1 and thus flows through the NPN transistor Q12 at the output side of the current mirror circuit M1. As a result, an electric current corresponding to a sum of I1 and I2 flows through the resistor R13 and at this time the output voltage VO on the output terminal Out can be given by:

VO =VCC -(I1 +I2)·R13 -VBE (Q15) (2)

In this case, a voltage drop through the resistor R13 becomes greater than the counterpart in the equation (1) and at this time a value of the output voltage VO corresponds to a value at the low level output time.

Here, ##EQU1## with VOL and VOH representing the output voltage VO at the low level time and output voltage VO at the high level output voltage VO, respectively, the equations (1) and (2) can be rewritten as follows: ##EQU2## where VBE (Q11): the base-to-emitter voltage of the NPN transistor Q11

VBE (Q14): the base-to-emitter voltage of the NPN transistor Q14

As evident from the equations (5) and (6) the output voltages at the high and low level output times can be freely set by a ratio of the resistances of the resistors R11, R12 and R13. Thus, the output voltage can be adjusted with high accuracy in obtaining an integrated circuit.

FIG. 5 shows an interface circuit according to another embodiment of this invention, in which two current mirror circuits M1, M2 are provided, one being constituted of two PNP transistors Q21, Q22 and the other being constituted of two PNP transistors Q23, Q24. In this case, an output voltage VO becomes equal to a value as obtained by subtracting a basse-to-emitter voltage VBE (Q15) of an NPN transistor from a voltage drop through a resistor R13. With an I2 L inverting gate G ON the output voltage VO becomes a high level VOH and with the I2 L inverting G OFF the output voltage VO becomes a low level VOL. The values of VOH and VOL are given by: ##EQU3## where VBE (Q21): the base-to-emitter voltage of the PNP transistor Q21

VBE (Q24): the base-to-emitter voltage of the PNP transistor Q24

Even in this circuit, the values of the output voltages VOH, VOL can be freely set by a ratio of the resistances of the resistors R11, R12 and R13.

An interface circuit as shown in FIG. 6 corresponds to a circuit as obtained by eliminating a current mirror circuit M2 and resistor R12 from the FIG. 4 circuit. In this circuit, with an I2 L inverting gate G ON an output voltage VOH at the high level time is fixed at a value VCC -VBE (Q15). With the I2 L inverting gate G OFF the output voltage VOL at the low level time becomes a value VCC -I1 ·R13 -VBE (Q15). In this circuit, only the output voltage VOL at the low level time can be freely varied by setting a ratio of the resistances of resistors R11, R13.

FIG. 7 shows an interface circuit in which the current mirror circuit M1 of FIG. 6 is replaced by a current mirror circuit comprised of two PNP transistors Q21, Q22. In this circuit, with the I2 L inverting gate G OFF an output voltage VOL at the lower level time is fixed at a low level i.e. at a ground level. With the I2 L inverting gate G ON, the output voltage VOH at a high level time becomes a value I1 ·R13 -VBE (Q15). In this circuit, only an output voltage VOH at the high level time can be freely varied by setting a ratio of the resistances of resistors R11, R13.

This invention is not restricted to the above-mentioned embodiments. Although this invention has been explained in connection with, for example, the case where two transistors of each of the current mirror circuits M1, M2 have the equal emitter areas, a greater or a smaller output current may be taken from the output side of the circuit with the emitter areas of the two transistors set at a predetermined ratio.

Instead of setting the ratio of the emitter areas of the pair of transistors constituting the current mirror circuit, a resistor R15 may be connected to the emitter circuit of one of a pair of transistors in the current mirror circuit as shown in FIGS. 8 and 9 and, by so doing, a greater or a smaller output current may be taken from an output side. Since in the circuit as shown in FIGS. 8 and 9 the resistor R15 is connected to the emitter circuit of the NPN transistor Q11 at the input side of the current mirror circuit M1, a greater output current is taken from the output side.

Sano, Jun

Patent Priority Assignee Title
4684831, Aug 21 1984 Applied Micro Circuits Corporation Level shift circuit for interfacing between two different voltage levels using a current mirror circuit
5656954, Nov 17 1994 Mitsubishi Denki Kabushiki Kaisha Current type inverter circuit, current type logic circuit, current type latch circuit, semiconductor integrated circuit, current type ring oscillator, voltage-controlled oscillator and PLL circuit
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Feb 15 1982SANO, JUNTokyo Shibaura Denki Kabushiki KaishaASSIGNMENT OF ASSIGNORS INTEREST 0039910641 pdf
Mar 10 1982Tokyo Shibaura Denki Kabushiki Kaisha(assignment on the face of the patent)
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